U.S. Pat. No. 3,617,270 discloses the use of squaric acid methine dyes for the optical sensitization of zinc oxide. U.S. Pat. Nos. 3,824,900, 3,837,851, 4,123,270 and 4,150,987 disclose the use of squaric acid methine dyes for a charge generation layer with a p-type charge transport layer in a multilayered electrophotographic plate.
U.S. Pat. No. 4,500,621 discloses electrophotographic plates containing squaric acid methine dyes in a binder, characterized by photoreceptive sensitivity in the infrared region.
It is an object of the present invention to provide novel squaric acid methine dyes which are useful as photoreceptors in single or multilayer electrophotographic plates.